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SmartSwitch ATM User Guide 6-5
Traffic Management Traffic Management Capabilities
6.1.3 Queue Buffers
ATM SmartSwitches perform buffering using a shared-memory architecture. Buffer space is divided into queues for
each class of service. In turn, ports are allocated a portion of each of the service class queues. This allocation is
controlled on a per-port basis by the
porttrafficcongestion commands.
Quality of service is defined on an end-to-end basis in terms of cell loss ratio, cell transfer delay, and cell delay
variation.
For example, enter the
show porttrafficcongestion command to view current buffer utilization.
SmartSwitch # show porttrafficcongestion
PortNumber(ALL) :
PortID QueueId ServiceClass MinIndex MinValue MaxIndex MaxValue
==============================================================================
CPU 1 CBR 10 64 15 1024
CPU 2 RTVBR 8 256 13 4096
CPU 3 NRTVBR 8 256 13 4096
CPU 4 ABR 8 256 12 8192
CPU 5 UBR 8 256 12 8192
PortID QueueId ServiceClass MinIndex MinValue MaxIndex MaxValue
==============================================================================
7A1 1 CBR 10 64 15 1024
7A1 2 RTVBR 8 256 13 4096
7A1 3 NRTVBR 8 256 13 4096
7A1 4 ABR 8 256 12 8192
7A1 5 UBR 8 256 12 8192
PortID QueueId ServiceClass MinIndex MinValue MaxIndex MaxValue
==============================================================================
7A2 1 CBR 10 64 15 1024
7A2 2 RTVBR 8 256 13 4096
7A2 3 NRTVBR 8 256 13 4096
7A2 4 ABR 8 256 12 8192
7A2 5 UBR 8 256 12 8192
PortID QueueId ServiceClass MinIndex MinValue MaxIndex MaxValue
==============================================================================
7A3 1 CBR 10 64 15 1024
7A3 2 RTVBR 8 256 13 4096
7A3 3 NRTVBR 8 256 13 4096
7A3 4 ABR 8 256 12 8192
7A3 5 UBR 8 256 12 8192
More(<space>/q)?:
MinValue
and MaxValue are thresholds set on a per-queue, per-port basis and are measured in cells (53 bytes). The
MinValue threshold is the amount of buffer space guaranteed to a call of a particular service class on the corresponding
port. The
MaxValue threshold is the maximum amount of buffer space that a call of a particular service class is allowed
on the corresponding port.
QoS corresponds to the queues as follows:
• Queue 1 — Constant Bit Rate (CBR)
• Queue 2 — Real Time Variable Bit Rate (rt-VBR)
• Queue 3 — Non-real time Variable Bit Rate (Nrt-VBR)